Method for converting hydrocarbon gases to liquid hydrocarbons



Sept- 75 1943. P. A. MAscHwlTz .ET Al. 2,328,829

METHOD FOR CONVERTING HYDROCARBON GASES 'I 'O LIQUID HYDROCARBONS Filed oct. 19. 1940 Patented lSeptrf?, 1943 This 4inventionrelatesto conversionof `hydroing by"the indirect heat exchangewith thech g t t carbonlgases to liquidhydrocarbonsand islmore,` ing stock; the reaction products are then'` choied particularly concerned withmethod for thermal to` a temperature sul@stantially-` beloivthe dew. conyerson ofhydroca'r'bon gases to hydrocarbons poini'tiziyy direct contactfwthiiqnid cooling me-` `boilingwithin the gasolinegrange; 5 durn. "Thefooling mediiiIn-'sedor the qiiench-Q` fllnthermal-gas. conVersionfpro-c'esses itis nect ing `should be aninertfiiquidwhich hasthef'abil` reaction 'zonei-n order 'to stop conversion. This rial such` asgdm;freeing` tar and aspi'ialt-'Whichl` may `bedone either Abyindirect'heat exchange o1 may Vcondense `from the reaction productsl-L`` Inf Dydirect quenching` with liquid." t :Both methods 10 thismanner deposition of carbonoricarbonaceous n `ttoelirtghavetheir advantages and*disadvem` materiarintheftransfer ntie is p reventedad the tages, "Indirectheateltchange permitsutilizaticny t l nateria4 which would otherwise depositin. the` t of the heat "remainingizi thlreaction prducts t heat exchanger` r transfer *lineis reinovefdfioln" to preheat thefchagping stockto a comparatively the system in liquid Sohitierr or suspension; hightemperatur'e, "thereby reducing fnelre'qnire` 15 t It'is an `object of this` inYenijQ w00" pijide Y ments "forheatingVV the charge to reaction tem Amethod "for utilizingthe heatin reaction prod#I l eratlire,A;greatdisadvantagedindirect copla"` vuctrsffromia gasconversionprocessoperated:at ling isjthatl` carbonand carbonaceous deposits l high PreSsureSwlWithOut caisnhilmfuldeposi` t 1b`ui1d""i1prapidlyin theftransfer line and Vhat tion' ofcarbonand carbonaceousfmaterial.y t ex`c`ir1ang`e1`"`,`v necessitatingfirequlent shutdowns for 20 It is *afurther-T Vobject'of theinventionfto "-j (Meaning,` Another disadvantage Adi indirect heat` `Vide methodfor preheating chargingstock ina "exchange is thefhigh `cost/ofthe exchangersgpar` t highipres'sure gas' conversion.yf r`ocess" by meansZ tcularly inhighpressuiebrocesses. f 4 otflhigh temperature#reaotionbrodcts ins'uchj Direct quenching Ywith liqid"V `eliminates or t manner' as to reduceithe' costlgf-theapparatusA gleatly'lessens Vthe deposition probiern, but fthe f25 t involved and aulsotoprevent clogging'of hthe" `quenched Vmixture is `necessarily at ajower'tem; t y paratussdue tocarbondepositon. Ane`1`"atureflevel *than the unqenched reaction "Otherlobjectsofztheivention'willtappear from` "products "and therefore cannot'possiblypreheatl` t `13h@ifOllOililg;iesrplr G'ille'ifIi,OILlilICSOIii the charging stock Ato agL high atemperattirek as with" they accompartying` drawing "offwhich the Vcan beobtainedfw'th theinnduenchedeactio 30 `Single gure is'ja*diagrammatic;sideelevatonal; ""products. *j 'y `view`offapparatus suitabieorcarryingout the It has been discovered that byfaproper com?A iI1V21f17I1-4 n f1 l t ".bination ofjfindirect heat 'exchange and direct Referring tothe dljf'twirlg, numeral A`lindicates quenching', thefdisadyantagesfof either'methodbfi t a linethroughwhichfresh gas'may be charged V cooling can be `obviated `and` the advantages of; 35 to thefsystern under pressure'b'y means of astute` f bothinalarg measure refalied. j `j ablecompressornot shown `Thefreshfgasinay Inaceordanee `'itnthepresentinvention, the be stabilizer g-'as Timm either or bthcta1ytc- Y; f pressure onthe hot reaction brdctsnleaving the" and! pyrolytiQOvl 'CEIGIIIIJr4 DFCfrLSQs nflXed CY reaction zone partiallyweducd and the reaq. unmix'edtwiththehigherihoiling'fractinsfof nat t tiont` products undef the"'lowersupefatmpsphefie 40 `mail gas. The-,fresh gas is passed through Water; i l pressurebut before reduetien in temperature are 0001er wherefhe temiieriaturmy `be reduced passed ih indirect heat' exehangeirelation with wapproximately 175" to-1009` F.- `The partially thev charging stock. "Thecoolingfby means 'f condensed gases pass to accumulator 5Which may t heat exchange with the `charging stoekfor Vother t be maintained wpressure'iof anproiilnnatt ly` veeolingmedidm tsreguiated sethat thetr'eaetion 45 20Go-250g1bs; fper square inch: Tht `:Qfntcriwif' preducts arejnet cooled tottemprature;sub.` megas `Witten isfnot1condens-eaisiwtthdrawn tantialiy below` the'dewf point Qfjthe mixture; `fromaccumulatorithoughthe 1,ne-'l" 'and passes Thedew point isthatftemperaturelat which drop,-V Y t from lignel 1 `thjrfmelril-linejSJ to thelowrjpbrtn `letsWofcondensibie material form and depositout of a low pres'sulebsoiberi l.l "Fresh gas linayhe fthe reactionniixttire"underthefpessurecon-l 50 fedJ into absorb'err Il` throughlinegl2t` "gas ditionsbengmaintained. By `limitingthe coolmay beiesduaij gas `from oil cracking ing toa'temperature'notsubstantally `below"the` l That'portion of the gas `whichdoes` AI idnefyis With-- dew point,deposition'oftcarbon o1"` cariconacecus"` Y, drawifroin the'accumuiatorilb? means of pump matter from thejwreaction `products ismfsubstan- "I3 thronghfline I5 intoeedtankji', 'IheffeedA mmediateiygfouqtving 1 l ytained-r1" maylupejmeinteined atA ptessurepf approxirnately 225 to 300 lbs. per Square inch rand at a temperature of approximately '75 to Liquelled gas iswithdrawnV from feed tank il through line I9 by means l,of pump 2l in which the pressure may -beL increasedhto F50-2000 or Amore lbs. per square inch, thenpassedthrough heat exchangers 23"'and 25 andline 21 to the inlet of the heating coil 29. In the heat 'exchanger i 23 the charging stock'may bepreheated to av temperature in the neighborhood of 200i F.*and in the heat exchangerc25 the charginggstockimay be further preheated to a temperature `in the neighborhood of L50 to 550 F. "Thef'preheatedigas isfurther heated in thev heating 4 coil129 to arcfr action temperaturev of 900 to" 1200F. and then passed to a reaction'coil 3li` in 'which the tem-"Lil peraturetofV the gases is maintained vv:for a suf.-

ficient period of time to bring about the" desired conversionl of hydrocarbon gases to liquid hy c drocarbons. The conversion ooil'kl is preferably. of greater cross-sectional `area than the heating coil in order tode'creasethe Velocity of the gases v undergoing reaction-and givethe gases sufficient time to react; The reaction coil y3l is'preferably placed in a zone Where `its temperature can be maintainedat the desired reaction-I temperature eithery by heating or cooling,y as required. vWhen;

the charging 'stock has a high concentration cf Y .o leflns, v the reactionV isexotherxnic in character,

necessitatingv coolingV of ythe tmixtureundergoing reaction.. f, However, where-,the concentrationof .golens-is low, the reaction isfendothermic in character, jnecessitating heating Vof the reaction C12hydrocarbons.,-, c f. Y c v'Ihe'hot reaction products leaving thereaction Y zone 3l pass through `the coil 33 of heatexchangc. ,e115 25 wherein the reaction products are partially Vcooled-by indirect heat exchangewith the chargel ing stock. Onek ofthe outstanding features lof thisinvention is thereduction of pressureon the hotreaction products prior to vtheir passage to the'fheat'iexchanger, by means of Vthe slide valve" `3 5. The pressure maybe. reduced at-Vthef-slide Valve to/approximately 500.-,600 lbs. pergsquareinch rwithout obtaining any substantial `amount of carbon deposition. By reducing the `pressure before the vreactiony products entergthe heat exvchanger 25, itlispossible vto utilize fat-.heat ex` 'changerv of cgmparatively low cost onconstruc-y tion instead-cran expensive heat exchangerwhich would otherwise be required t'o withstand the high pressure and temperatures :to which itwould bel subjected. .1nl the heat exchanger the temperaturelof 'the raction products is reduced toa temperaturenot` substantially below thejdew point u of the ymixture. At` pressures .ofj500 lbs. per f squarefinch and higher ,the dew pointy will be within-the temperature rangerof approximately`r Milliy t o"7:5,0 .F.j It Will be understood-that it Iis notgnccessary to reduce. the, temperature of the reaction.products in theheat exchanger'25 to the dewpoint, but in order to obtainlthe benet o f'asmuchof the heat inthen'reaction 'prode notsas possible` for n preheatingA rthe charging stock, itfis preferred thatthe `temperature of the I Imm'ediatelyfupon yleaving the heatY exchanger K coil`33,` the partially cooled reactionproductsare further cooled by injecting cooling iiuid into the stream of reaction products at the point 3l. The temperature to which the reaction products are quenched by injection 0i cooling liquid is substantially below the dewpoint of the reaction' i mixture and in practice vis preferably Vbetween r v 250a`nd 50.0 F. 'Suicient` quenching fluid of rhigh enoughboiling point vmust be used in order to have a substantial `body of liquid present to #carry in solution or in suspension any high boil-k ing material of a gummy, resinous, tarry, asphalfg tic or Ac'arbonaceous 'nature which precipitates from the reaction mixture.

The reaction mixture which has been Vcooled fbelowits` dew point'rmay be further cooled if necessary, by passing through water cooler 39 in whichk the ltemperature is lowered to approximately 250 to 350513. From the cooler S9 the products pass into the lower part of fractionating Y vtower 4l.

The fractionating tower Mis maintained under such conditions that onlyl C4l and lighter gases passoverhead'. r-Tofaccorn'plishthis fractionation, the tower maybe maintained Aun f der the pressure tof'which the reaction products,

are reduced at the .valve B5, allowing for pressure u drop through the'line, with a bottom tempera-t.

ture of 250 Rand a topltemperaturefof about 200" F. The pressureinthe tower maybe in-the y neighborhood -of .400 lbs. per square inch. IUnQ der these conditions substantially 1allthe C5 and` heavier hydrocarbons as well asar part of the lighter hydrocarbons condense-as aliquid inthe bottom of the tower. A portion of the condeng sateiscwithdrawn from the bottom .of the tower the heat exchanger 23and cooler-45 Vthe condene-fv M V; sate used for quench'. may beV cooled to a -temperature of approximatelylO? to 200 F. Thev remainder of the condensate isA withdrawn from*A through heat exchanger. by means of jpump d3,

,passed through water cooler and line tl and injected as 'the quenching `liquidinto the reaction ystream at the point 3L` In vpassing through the bottom of ffractionating-tower 0l through line 49, controlled 'by Valve 5l and passed to stabilizer 5 5., The pressurev is somewhat reduced` at the Valve 5|, but thepressure in the stabilizeris pref-- v erably mainatinedy above 100 lbs. per square inc h line 55 into reboilerk 5l'. Vapors ironithe rereactioniproducts ai;v this stage v should-'bec 1reyduced asiclose toy the .dew pointasjposs'ible.. ,Y c

tof"insureliquefaction oftherecycle gas. In the` stabilizer 53 any gases lighter than Ci and a. portion or all of the C4 hydrocarbons are removed f f from, the condensate. Heating of-the condensate-in the stabilizer, is Aaccomplished by passing itgfromthe lower portion ofthe stabilizerthrough boiler 'are returned to the stabilizer through line 59. The stabilizer 4condensate is withdrawn from the reboilerfthroughlir'e 6l and is sent to storage vor toY a're-run operation of make finished gasoline. The vapors frornvthe stabilizer which are composed chiefly ofCa and-0 4 hydrocarbons, with small amounts of lighter boilingmaterial, pass overhead throughline l'through cooler65 wherein a portionof the gas condenses and then passes to accumulator 6l. -Theliquid from'the accumulator 6l is recycled lby means of pump 69 and Vline ll `to thetop of the. stabilizer 53 asre.

iiux liquid. The gasesfrorn the accumulator 6l y are'takenoi throughl line 13.toanother water cooler 15 where the-temperature is reduced toapproximately .to 100f,"F..and `substantially allof the gas condensesto'liquidand is collected infine accumulator n.1 The Smau. amount vof gas'V which doeswnot condensel is withdrawn through line l9,controlledbyl'jvandmayrbeiref` cycled to the low pressure absorber or `withdrawn lily` the `same pressure asthV higli pressure,.ac-"

` absorber is preferably runat a pijessur ""rent to the gas passing lul'awardly therethroughr4 The major portion of the C4 and Orgases as Well i vene., hydrogen and c2 hydrooorbonsis withdraw@ n yoreive |249,` and from `euoeoruoer; lvlithroughb lihe I3I1, controlled-by rval've |33, arieleliminated` t g, I 2,328,829 fromme system. Accumulator- 11? is `prefereuoizyfi t meintomedlunder a pressure of `100 toffzoo i 'flieliqueedf gas `collected `in accumulator 'Il `is 51 l 85 and-returned to aouniulatr 5 together with thfesh' feedzl Y f 1 l j k "Returning tothe mainfractionating tower 4|,fg

\ they@ and lighter 'eases are i taken oierheadr 1o i throughline 81, coplelbypassing'through vsratery cooler M89 to a temperature of approximatelyl ""3 `lqancl thengpassedY to accumulator 9|.` Aportioh I oflthe" gases arecondeusedin passingthrouglfii i fcooler 89. `The liqueiied kgasis withdrawn `from ""th'e aecumulatorl by means Vof;.pu1frip`93 andi-re? Qyledthr-Qugh lines S15 and M91, cnmlldby valve 09, tothe top of the xfractionatingtower 4| l, asureilux liquid. A` portion of the` liquefied` gas freni accumulator SIHmaybepassed throughlirie 20w `I||| to the top of flash-tower |03 as reiluxliquid. "The unconclensed` gas 4fromaccurnulatoi;:Sti lisv `withdrawn `through liner` |105` to =a second water eooler |01 Wheregthe temperatureistfurther rbi-ifn v 'ducedto approximately 90'* vtolOO; l".[z-ithe 2;' Y cooler |01 alarge portion of 4thegas,condenses' o toliquid under the existing pressure Whihd is i r substantially thatmaintained in the ractionatn ingutower 4|. The cooled products passirom cooler4 |01` to accumulator |09 `from ,which the 30. liqueedgasis withdrawn through linerIyII, con-` i trolled by yalVeIIS; to leed'tarilll"Ij The .pres- Y deeudruieeor-` meebrengt imei |215` fend; @wreed` .I to "theV lower portion ofrrhiglh pressure absorber MCI;` Thisabsorber` is fmaintainfecl atlsubstafnti eumulato'rryIOS; being slightlylowerbec'ause of "pressure "drop l through. the line@` :When the frac "tionating tower 4| is 4rnaintaiued atainpressuref offgabout 410 lbs. per square. inch, .the high"pres-M throughlline 9 tolow pressure absorber-jf` p Abeorpuoomenstruum,such ds iight gestion or'- mineraisei ou isy oharged to kthe )lopery 'portion "ofebsorbers add n1througniinesuserid.55

|2551` respectively. Absorption mens'truum" passes f downwardly throughthe ebsorbersoounterouref es` esubstantieiporuootof theico ioydrofodrigore` o .""land lasmall anount of rriethaneisf absorbe@by `g `the absorption menstruurn in .thel tfWo absorbersg` The unabsorbed gas .consisting `chiefly of rhethj from the` system `through line; |35. i The] rich` derleduired. 1

` p'eferablyfihaihtained iatxsuiiicient pressure o`` enable returnof thgastothe low pressur abfrohithe bottoniof lowrvpressurefabsorber IaI through line |40 by"`meansl of` pump I4I .nd f passeiiwthrough heatexchanger |43sto the lo'wer portionofflashtower |03. `Thelpres'suie on the richlmeiistruumiis `raised in the pump ,|41 to l a pressure slightly higher than that maintained1 .e in th'e accumulator 9|. Inllpassing through` the ization inV thewilashtower |03 oftherlighter'g'as the? .bottom of""f1ash'tower ma uirough'ime m, t controlled by valve |49, andpd'ssed to the midportiohof stripper Ill'. "The pressure o the parf tower may be ina'intaihed'at a" pressure onlysufcientto" enableretlirh of? 4gases to the low pressure absorbertwith'out compressiorl.4 Theliquid in'thebottorn of the stripper I5|Uis Withdrawn vtemperature slightly below"`600 Ff, is`witlcirawri1b system "througnime ieaeontrolied by voivef m, "The :stripped ges-es dre removed' from the top of stipperillrtbiough line=|'|3,` cooled'to a lteijfimaininggasesfaretaken froxri the accumulator cl'erilsed materialpasses to lo'w pressure accumulatorhl'l. The liqueed`gasfrom the" a'celr-j` muiotor "m1 'ijs charged throng-'nj mie Amafbyineer'rs i 4 productsr into theitower. Theunconolensed gas is withdrawn froth'the-lowpressure accumulator Ilfa'hd returedf through line |93 Vto the low. pressure 4absorber II.` `The accumulator |81 The oombirred rich' menstruum with-drawn Aipor'tion 'of the 'gesfesrer'e condensed residueandy stabilizer- .gas from yhigh pressure,

pyrolytic cracking' of'h'ydrocarbon oil, is used-as the-freshcharge to the system. The stabilizer `gas iscooled in .coo-ler 31to 'a temperatureof 95 F. and the laccunnilator is maintained at a presl sure lof 230 'lbsj'per square inch.. vl'eedftank |1- ismai'ntained :at atemperature of 90 F. and a pressure of 265 lbspper square inch. 'Residue gas is charged to the low pressureabsorb'er ,l l. The analysis f of .the. combined stabilizer and residue gas charged tothe Process in Inol.upercent is asv follows;

Hydrogen l r 3.6

The oleflnencontent ofthecombined gas isv ap-y I proximately before treatrnent-r inthe absorbers and the olefin content-of .that portion of 1 the combined fresh gas which is charged to the reaction coil is 40.75%.

I Jqueed gasyfrom the the following compositionin mol;l percent:

ischarged to theheating coil '29 under pres-,

sure'off12501lbs. per square inch and preheated toatemperature of 500 F. by passage through the' exchangers 23 and 25. In the heating coil 29 the temperature ofthe charge is raised. to 1060","F. and this temperature is maintained in l the reaction coil 3|. -The pressure at theslide valve 35 is reduced to 570 lb s. ;p ersquare-inch feed tank` Al1 having.

Propene v f Propane f "'1 7.7 Butenfes j' k'7. 5 Buta'nes i 8.2 i Pentanes and pentenes 0.9 Hexanes and hexenes j 0.8

As anexample of .actual yoperating conditions, pressure of 1901bs. persquareinch with a bottom;

temperature of"590 F. anda `top temperat ure oi y .29.0.YF.- I he accumulator |11 isA maintained ata`A temperature of v 21m-.112,and the low pressure `.acb cumul'ator |81 maintained ata temperature-ofiv 95F. and a pressure :of 180lbs. per square inch.

`'I'he'total.residue gas leaving the systemwill have the following composition in mole percent:VV

- This reccle ratio,' thatis'fthefratio of the higher boiling hydrocarbons; will be 5`to 1.

lit'v will be seen that "inaccordance- With'this invention it is possible vto Aoperate under extremely high pressure conditionsand utilize the heat ofv the reaction products for heating the charge without the necessity of usingl expensive heatex' changers, due to the discovery that reduction in* pressure on theV reaction products can be accomplished before cooling without'causing excessive deposition and clogging in ythetransfer line and heat exchanger.l Y' It isclaim'ed:A i 1.v In the process of converting hydrocarbon gasesto liquid hydrocarbons at high superatmospheric pressures and at high temperatures be `tween approximately'900 and 1200" F., the'steps ofv and' thev temperature is reduced in the heat exchanger 25 to 700 F. A pressure drop takes place through the heat exchangercoil 33 sothat the pressureon thefoutlet is only 420 lbs. pers quire-` inch. v*The partially cooled reaction lproducis are quenched to a temperature vof 450 F. byvineans f ofv condensate withdrawn from the fractionating tower which had been cooled to 180 F. and the temperature of the reaction products is `further lowered in the cooler 39 to r320" F. The fractionating tower 4| is held ata pressure of 410 lbs.

per square inch with a bottom temperature ofr 2501E".v and a top temperatureof 195 F.. The accumulator 9 is held at a, temperature of V155 F.

. and. accumulator |09 ataternperature of 95 F.

The pressure in both is 400 lbs. vper squareinch.`

Accumulatorv 5 is held at a pressure of 230 lbs. per square inch and a temperature of. F. bilizer 5311s maintained at afpressureof lbs.,

i per square inch with a bottom temperature of` 330 F. and 'a top temperature of 140 F. y ,y

'The vlow pressure absorber is v maintained at. a

` pressure of'1'75 lbs. per square inch and thehigh Y pressure absorber is maintained at 385 lbs.. per i square inch. 'Flash tower |03 isfmaintained at a l ,pressure fof`410 lbs. per square inch with vthe in comingrich menstruum heated to ar` temperature of 390 F. The stripper 15| is maintainedatga:

Sta-

reducing the pressure on the reaction products at the outlet of the reaction zone to a lower superate i mospheric pressure; then cooling j the reaction products toa temperature Vbelow conversion teniperature close to butnot below the' dew` point or the reaction products by indirect' heat exchange i with charginggases, then suddenly cooling the re-f o action products from a temperature notsubstan` tiallybelow the dew pointof the mixture toa-tem.-l perature substantially below the dew point by direct ,contact with cooling liquid ofsuch nature as to hold suspended material contained in the re.

action products in solution or suspension.

2.A Method in accordance with claim` 1 in: which the hydrocarbon gases are cooled by indirect heat interchange to a temperature not less rthan approximately 650 F. and the partially cooled re'- action products c'ooled substantially below 650v F. by direct contactwith cooling liquid.

"3. Method in accordancewith claim v1 in which thefgases are converted atapressureiabove'7501 lbs. per square inchand the pressure on the'productsr at the outlet of the reaction Zone is reduced toapressure not in excess of600 lbsper square l inch.

4r.' Method in accordance with claim 1 in which thegases are converted at temperatures labovev 900fF. and pressures above '750 lbs. per square:`

inch', the pressure on the reaction products is refduced at the outlet of the reaction zone to a pressurefsubstantially below '750 lbs'. per square inch,V

thefrreaction products are; thereafter partially:

cooledto a temperature below .Conversion but not substantially below 650 F. by indirect heat exchange andthe partially cooled products further cooled to a temperature substantially below 650" F. by direct contact with cooling liquid.

5. In. a process for converting hydrocarbon gases to liquid hydrocarbons under highipressure and temperatureof the order of 900-1200" F. in a conversion vzone and in which the reaction prodnot below the dew point of the mixtureby indit c not substantially below the dew point ofthe reaction mixture to a temperaturesubstantially be. low the dew point by direct Contact with cooled liquid condensate. t i t 6. Process in accordance `with claim'5 in which the conversion Zoneisk maintained at atpres'sure i above 75D lbs. per `square inch andthepressure 15 f rect heat exchange with charging `stockjfurther l cooling the reaction mixture from attemperature inch priorto cooling;l l Y y t 7. Process in accordancewithclaim 5 in which the `ractionproducts are cooled to a temperature between 6507 and 800 F,"by indirect heat ex- `change `with charging stock and the reaction products are chilled subst'antiallyhelow"650 F` `by direct Contact with cooled condensate.

t V8. Methodinl accordance With claim 5 in which ;the'condensate used for cooling the reaction prod- 1 uctsfis 4cooled by indirect heateichange with charging stock prior to passing the charging stock in indirect heat `exchange with reaction products.

is reducedbelow approximately 600 lbs. per square i 

